1. Field of the Invention
The present invention relates to a television image processing apparatus for outputting image data to large-screen display in accordance with a display format.
The large-screen display is one that is disposed in large-scale institutions such as baseball fields, gymnasiums and the like.
2. Description of the Related Art
FIG. 1 shows a conventional large-screen display system which comprises a display 10 and a TV image processing unit 12. The display 10 includes a display panel 15 on which plurality of light emitting elements 14 are arranged in matrix with a group of drivers 16, each for driving the corresponding one of the light emitting elements 14.
On the other hand, the image processing unit 12 comprises a sampling section 18 which receives an analog TV signal and converts the analog TV signal into a digital image signal which is in turn outputted therefrom to the display 10. The image processing unit 12 also includes a timing controller 20 which provides a clock 100 to the sampling section 18, and at the same time a timing signal 102 to the display 10.
FIG. 2 shows the detailed structure of one driver 16 in the display system of FIG. 2. This may be one that is described, for example, in Japanese Patent Laid-Open No. 56-4185.
The driver 16 includes a down-counter 22 which receives 6-bit image data 103 from the sampling section 18 shown in FIG. 1. The down-counter 22 also receives a setting signal which is the timing signal 102 outputted from the timing controller 20 (see FIG. 1). When the down-counter 22 receives the setting signal 102, the 6-bit image data 103 Is loaded into the down-counter 22. At the same time, a flip flop 24 is switched on by the setting signal 102. Thus, the down-counter 22 begins to count the number of clocks 104. If the counts of the down-counter 22 reach the number of bits in the loaded image data, the down-counter 22 then outputs a coincidence signal to the flip flop 24 which is in turn switched off by the coincidence signal.
In such a manner, the corresponding one of the light emitting elements 14 will be lighted on only when the flip flop 24 is in its ON state.
Since the image data 103 has 6 bits, the time through which the light emitting element 14 is lighted on can be set in sixty-four steps.
In FIG. 1, each of the light emitting elements 14 is a lamp for emitting a light with either of three primary colors RED, BLUE or GREEN, these colored lamps being suitably arranged to form the display panel.
Since image data is provided in parallel from the sampling section 18 to all the drivers 16, the conventional large-screen display system as shown in FIG. 1 must perform the high-speed transmission and control of the image data.
An improved large-screen display system which intends to overcome the above-mentioned problem has been proposed, such that described by Japanese Patent Laid-Open No. 60-237774. Such an improved large-screen display system is illustrated in FIG. 3. The display system comprises a display 26 which is divided into three horizontal blocks 26a, 26b and 26c. Each of these blocks includes a plurality of modules 28 each of which includes a number of drivers and a number of light emitting elements, as described with reference to FIGS. 1 and 2. In each of the blocks, the modules 28 are connected with a bus 30.
The display system also comprises a TV image processing unit 32 which includes a sampling section 18 for receiving an analog TV signal 106 and outputting digital image data for each of the color components and buffer memory sections 36a, 36b and 36c, each located therein for the corresponding one of the blocks 26a, 26b and 26c. The sampling section 18 receives timing clocks 100 from a timing controller 20 in the image processing unit 32. The imaging processing unit 32 further comprises buffers 44 and terminators 46, all of which are disposed within the respective blocks 26a, 26b and 26c.
FIG. 4(a) illustrates a TV signal 106; FIG. 4(b) illustrates image data digitized in the sampling section 18; FIG. 4(c) illustrates a portion of the image data which is enlarged in the direction of time axis; and FIG. 4(d) illustrates clocks 108 outputted from the timing controller 20.
As can be seen from FIG. 4(c), the sampling section 18 outputs image data for each of the color components. In each of the image data, the forwardmost letter "R", "G" or "B" indicates the corresponding one of the color components. The third letter "1" indicates the first field in the display and the fourth and fifth letters represent serial addresses for the respective color components.
FIG. 5(a) illustrates an analog TV signal 106 in which the effective period 110 within one horizontal scan period H is divided into three sub-periods H.sub.1, H.sub.2 and H.sub.3. FIG. 5(b) illustrates various ranges of time in the image data stored in the buffer memory sections 36a, 36b and 36c. More particularly, the buffer memory section 36a stores image data within a time period W.sub.1 ; the buffer memory section 36b stores image data within another time period W.sub.2 ; and the buffer memory section 36c stores image data within still another time period W.sub.3.
The image data stored in each of the buffer memory sections 36 is read out from a time period P.sub.1, P.sub.2 or P.sub.3 following the respective one of the writing periods and supplied to the corresponding one of the blocks 26a, 26b and 26c through a bus 40.
As can be seen from FIG. 5(b), the read-out of image data from the respective buffer memory sections 36 can be performed with a sufficient time at a relatively low speed. Such an arrangement is thus advantageous in that the buses 30 may be constructed as by the use of flat cables having less high-frequency characteristics.
As the stored image data is read out and outputted, each of the buffer memory sections 36 functions to add an address number data with respect to each scanning line to the leading end of that image data. Based on such an address number data added to the leading end of the image data, therefore, each of the modules 28 can judge whether or not the image data is one transmitted to itself.
The display system 26 operates in an interlaced scanning mode as in the prior art.
FIG. 6 shows two typical display formats in the prior art, wherein one display format denoted by (I) is defined to be the first display format while the other display format designated by (II) is defined to be the second display format.
In FIG. 6, a character-string in each of the boxes represents an address of the image data applied to the corresponding one of the light emitting elements. More particularly a character-string "B0101" shown by 200 in FIG. 6 indicates a blue color by the character "B" and an address of the first image data at the first field by "0101". This data corresponds to the image data 200' shown in FIG. 4(c).
In FIG. 4(c), only the image data "B0101," among the first image data for the respective colors, is used with the remaining image data) "R0101" and "G0101") being discarded. In other words, the first display format is adapted to a large-screen display including a relatively small number of light emitting elements and more particularly to a display including up to about 640.times.480 pixels. With the TV signal being in the form of an NTSC signal, if the number of light emitting elements measured in the direction of horizontal scan on the display is equal to 640, the frequency in the sampling clocks 108 may be equal to about 12.5 MHz.
In order to accommodate for more than 640.times.480 pixels, the first display format must use the sampling clocks at a higher speed. In such a case, however, the speed of the sampling clocks becomes higher than the transmission speed of the image data passed through the bus 42 shown in FIG. 3. This raises a difficulty in transmission of data.
Thus, the second display format is currently utilized. As can be seen from FIG. 6, the second display format (II) comprises a plurality of light emitting element sets, each of which includes four light emitting elements or pixels R, G, G and B. When a TV signal is sampled, image data for the respective color components is simultaneously displayed at the same sampling point. In other words, the second display format effectively utilizes the image data of all the colors. Even if the second display format uses the same speed of sampling clock as in the first display format, a former may adapt to a display having the number of light emitting elements four times that of the first display format. It is to be noted that the second display format provides and simultaneously displays the image data of green to two light emitting elements.
In the prior art, thus, one of the two display formats was selected depending on the number of light emitting elements used in a large-screen display. Thus, the large-screen display system used a TV image processing apparatus of the type corresponding to the selected display format.
Recently, large-screen displays are being installed in various types of out-door and in-door institutions such as sports stadiums, gymnasiums and the like. The large-screen displays are dimensioned depending on the application for which they are to be used. A display format is selected depending on the size of the large-screen display used therein.
However, the television image processing apparatus used in a large-screen display system can adapt only to a display format which has been selected therefor. For another large-screen display having a different size, a different television image processing unit must be designed and manufactured. This results in an increase of manufacturing cost and becomes an obstruction that prevents large-screen displays from spreading. Since they attach importance to the provision of information based on images, it is desirable to provide a television image processing system which can be used in large-screen display having different sizes without any modification.
It is therefore an object of the present invention to provide a television image processing system which can selectively adapt to a plurality of display formats.